Elsevier

Vaccine

Volume 30, Issue 37, 10 August 2012, Pages 5527-5532
Vaccine

Potential impact of parental Tdap immunization on infant pertussis hospitalizations

https://doi.org/10.1016/j.vaccine.2012.06.047Get rights and content

Abstract

We estimated the potential impact of parental Tdap immunization before delivery, at delivery and at the 2-week newborn visit on U.S. infant pertussis hospitalizations. We used published data for pertussis hospitalization rates among U.S. infants aged 0–4 months, the Tdap vaccine efficacy in adults, and the proportion of infants with pertussis <6 months of age in which either parent was the source (16–40% from mothers and 16–20% from fathers). Immunizing parents before pregnancy or ≥2 weeks prior to delivery should reduce pertussis hospitalizations among infants 0–4 months by 2694–9314 if both parents are vaccinated, and by 1347–6909 if only mothers are vaccinated. Greater reductions in pertussis hospitalizations would be achieved if parents are immunized ≥2 weeks prior to delivery than after delivery or the 2-week newborn visit. Although immunizing parents prior to pregnancy or delivery is best, immunizing parents in the postpartum period should provide protection to that newborn and to infants of subsequent pregnancies.

Highlights

► Young infants have the highest morbidity and mortality from pertussis. ► Parents are a common source of pertussis for young infants. ► Immunizing parents and household contacts with pertussis vaccine is recommended. ► Immunizing parents should reduce infant pertussis hospitalizations by ≥9–14%. ► Parental Tdap immunization may also benefit infants of subsequent pregnancies.

Introduction

Despite the tremendous success of immunization programs, pertussis remains a poorly controlled, vaccine preventable disease. The incidence of infant pertussis hospitalizations and deaths has increased since the 1980s, suggesting increases in disease rates rather than increases in disease reporting [1], [2], [3], [4]. Reducing pertussis disease rates among children, adolescents and adults is an important public health goal given the severity of this disease among infants too young to be fully immunized.

An important approach to preventing pertussis hospitalizations is to immunize persons most likely to transmit pertussis to young, vulnerable infants, the age group with the highest rate of pertussis hospitalizations [5]. Transmission from family members is common, and mothers are the most commonly identified source of infant infection [6], [7], [8]. A “cocoon” approach to infant pertussis prevention, in which close contacts of infants are immunized against pertussis, is an attractive way to interrupt transmission. Several approaches to effectively implement pertussis cocooning have been studied [9], [10], [11], [12].

There has been recent, heightened awareness of the burden of pertussis disease in adolescents and adults. In 2006 the U.S. Advisory Committee on Immunization Practices (ACIP) recommended that a single dose booster of combined tetanus, reduced-dose diphtheria, and acellular pertussis vaccine (Tdap) be given to adolescents and adults <65 years of age [13], [14]. Further, the ACIP has recommended that Tdap vaccine be administered to women before pregnancy, in the third trimester or after week 20 of the second trimester of pregnancy, or in the immediate postpartum period, and to household and caregiver contacts of young infants [14], [15]. Tdap is highly effective in preventing pertussis in adolescents and adults. In 2010, 11% of U.S. adults with infant contact had received Tdap [16].

Infant pertussis disease is potentially life-threatening, variable in clinical its manifestation, difficult to diagnose, and a significant threat to health worldwide. Enhanced Tdap coverage of parents of young infants will reduce infant pertussis hospitalization rates. Three approaches have been studied to enhance parental Tdap coverage – during pregnancy, during birth hospitalization, and at the 2-week newborn visit [9], [12], [17], [18], [19]. We sought to estimate the potential impact of parental Tdap vaccination for each of these three approaches on rates of pertussis hospitalizations among U.S. infants, using published data on infection source, hospitalization rates, and Tdap vaccine efficacy.

Section snippets

Methods

The assumptions used in this analysis are summarized in Table 1, and include estimated rates of U.S. infant pertussis hospitalizations for 0 to <1 months, 1 to <3 months, and 3 to <5 months of life from 1980 to 1999 and from 1993 to 2004 [1], [2]. These rates are comparable to other U.S. estimates and are lower than the rates reported from Australia, Canada, France, New Zealand and Spain [3], [20], [21], [22], [23], [24], [25].

Infant pertussis hospitalization rates after the 2006 ACIP

Results

The projected number of U.S. pertussis hospitalizations in 0 to <5 month old infants is 9151–18,779 (see Table 1 for interval breakdown). The estimated number of pertussis hospitalizations prevented among infants in the 1st month of life varied dramatically for each scenario (Table 2). For parents immunized ≥2 weeks prior to delivery, during the birth hospitalization, and at the 2-week newborn visits, respectively, infants in the 1st month of life were fully protected, protected for later half

Discussion

Immunizing adults with Tdap represents a significant opportunity to reduce the incidence of severe infant pertussis disease. The determination to reduce pertussis disease overall and severe infant pertussis has driven recent ACIP recommendations for broadened Tdap immunization of adolescents and adults and includes pregnant women after week 20 of the second trimester of pregnancy and postpartum women [13], [14], [15]. Programs that specifically target parents for Tdap vaccination have been

Acknowledgements

The project described was supported in part by K23AI65805 from the National Institute of Allergy and Infectious Diseases and the Wachovia Research Fund. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Allergy and Infectious Diseases or the National Institutes of Health.

We thank Bobby and Jenny Peters and all the children that we have treated with pertussis and their families who inspired this work. We

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